This invention relates to a method for supplying the lubricant (i.e., lubricating oil) to a rotational-part supporter that is employed in a rotational device such as an electric motor or a spindle.
Grease lubrication is a method for applying a fixed quantity of grease onto bearing members when the bearing members are assembled. According to this method, since the machine is operated almost without later grease-resupply, almost all the grease applied when the bearing members were first rotated is scattered to their surroundings, and, as a result, the grease left on the track surface is very small in quantity. Therefore, the bearing members cannot be rotated for a long time, and, in addition, their lifetimes are highly unstable.
Oil mist lubrication is a method for lubricating a rotational part of a bearing while spraying oil misty onto the rotational part by means of compressed air. According to this method, heat generation can be reduced, and the bearing can be used as a high-speed rotatable one. However, a problem resides in that an exclusive oil mist generator is needed, which raises costs, and in that the emission of exhaust gas that includes oil contaminates the surrounding environment.
Oil air lubrication is a method for lubricating a rotational part of a bearing with a small quantity of oil by means of compressed air. According to this method, heat generation can be reduced, and the bearing can be used as a high-speed rotatable one. However, a problem resides in that an exclusive oil air-lubricating device is needed, which raises costs, and in that the emission of exhaust gas that includes oil contaminates the surrounding environment.
Jet lubrication is a method for pouring a large quantity of cooled oil onto a rotational part of a bearing. This method is superior in cooling, and is used for high-speed rotatable bearings. However, disadvantageously, very great power is required to rotate a shaft, and machine costs are high-priced as the machine needs a large quantity of oil that is controlled at a constant temperature. Therefore, this method is applied only to very limited uses, such as bearings of an aircraft engine.
As described above, all of the conventional methods of lubricating a rotational-part supporter have both merits and demerits. Generally, the quantity of the lubricant to be supplied increases as the speed of the rotational bearing increases.
However, the prior art according to the aforementioned methods has no basic construction in that the quantity of the lubricant to be supplied is properly varied in accordance with a variation in rotational speed.
In consideration of the above circumstances of the conventional methods, the present invention aims to provide the basic structure of a lubricating method capable of supplying an appropriate lubricant in accordance with a variation in rotational speed of a rotational bearing.
In order to solve the aforementioned problems, the present invention has a rotational-part lubricating method in which, in a rotational-part supporter in which one of either the inner or outer parts is fixed, and the other one is rotated, and a main rotational shaft lies between the inner and outer parts, a predetermined quantity of the lubricant is supplied to a rotational bearing at predetermined time intervals, and either the time interval or a supply of lubricating oil at one time is adjusted or, alternatively, both of them are adjusted in accordance with rotational speed.